The present invention relates generally to a sole structure for a shoe, and more particularly, to an improvement in the sole structure for enhancing cushioning and bending properties of the heel portion of the sole.
Japanese patent application laying-open publication No. 2003-339405 shows a sole structure for a shoe to secure cushioning properties of the heel portion. In the sole structure, an upper plate and a lower plate are disposed on the upper side and the lower side, respectively, of a wavy plate that is disposed at the heel region.
In this case, a plurality of voids formed between the wavy plate and the upper and lower plate function as cushion holes to secure cushioning properties of the heel portion.
However, in the prior art structure shown in JP publication No. 2003-339405, since the upper convex portions and the lower convex portions of the wavy plate are fixedly attached to the upper plate and the lower plate, respectively, a vertical deformation of the wavy plate has been restricted at the time of striking onto the ground. Therefore, the prior art structure had the limitation on improvement in cushioning properties of the sole heel portion. Also, in the prior art structure, restriction on the deformation of the wavy plate has impeded the bending properties of the heel portion as well.
On the other hand, Japanese patent application laying-open publication No. 2003-9906 shows a sole structure for a shoe having an upper wavy sheet and a lower wavy sheet that are oppositely disposed via a void between an upper midsole and a lower midsole in the sole heel portion.
In this case, the void between the upper and lower wavy sheet functions as a cushion hole to secure the cushioning properties of the heel portion.
However, in the prior art structure shown in JP publication No. 2003-9906, since there are provided the upper midsole on the upper surface of the upper wavy sheet and the lower midsole on the lower surface of the lower wavy sheet, the upper and lower midsole restricts the vertical deformation of the wavy sheet at the time of impacting onto the ground. Therefore, the prior art structure had the limitation on improvement in cushioning properties of the sole heel portion. Also, in the prior art structure, restriction on the deformation of the wavy sheet has impeded the bending properties of the heel portion as well.
An object of the present invention is to provide a sole structure for a shoe that can improve bending properties as well as cushioning properties of the sole heel portion.